1. Field of the Invention
This invention relates to an inverter with short circuit protection.
2. Description of the Prior Art
Industrial voltage source inverters generally consist of a DC voltage source such as a mains rectifier and smoothing capacitor connected to outputs by switching elements which are driven by Pulse Width Modulation control signals to generate the required output voltages. These circuits require short circuit protection to prevent damage to the components if the outputs are shorted.
Short circuit protection is often provided by the use of current sensors which allow closed loop control of the output current. It is necessary to ensure that these sensors are powered and operational before the outputs of the rectifier are enabled.
Inverters have upper and lower outputs and bootstrapping is used to provide power to gate drivers of the upper output. Bootstrapping involves the use of a diode between the gate drive power supply and a supply referenced to the negative DC link. This cannot be used however if phase current monitoring is employed since the current sensors will not be powered up until after the output devices are switched on. EPO431492 describes such a device.